This invention relates to product applications for substance encapsulating laminate webs. More particularly, this invention to a laminate web wherein at least two outer layers sandwich or encapsulate a powdered, granular, particulate, or gel substance or a central layer. In preferred embodiments, the multilayer laminate web is apertured.
Laminate webs formed by the joining of discrete webs in a layered relationship are well known in the art. For example, often laminate nonwoven webs are utilized in disposable absorbent articles such as diapers and adult incontinence products. Such laminated webs can be used as a topsheet, backsheet, or side panels. One example of a laminate web is a film/nonwoven laminate useful for a stretch side panel of a disposable diaper. Nonwoven/nonwoven laminates are also utilized to provide additional bulk or softness to a web component. Likewise, film/film laminate webs can provide benefits by combining the characteristics of various films in a layered relationship. Laminate webs can also be called composite webs.
Less common examples of laminate webs include laminates of dissimilar materials. The materials may be dissimilar in mechanical tensile properties, thermal properties, or visual/tactile properties. For example, a nonwoven web may be joined to a relatively stiff fabric to provide for a soft surface feel to the fabric. The dissimilar materials may be joined by melt bonding, adhesive bonding, ultrasonic bonding, and the like. Bonding methods are often determined by the materials themselves, but often require adhesive bonding. For example, a laminate or composite of materials having widely differing melt properties may require an adhesive layer between laminate layers. Even materials having similar melt properties, such as nonwoven and thermoplastic film materials are often joined by adhesive for adequate bonding to prevent unwanted delamination. Although adhesive may be necessary, such processing methods can be expensive due to the addition of adhesive, and the resulting laminate is often relatively stiff, depending on the laminate materials and the level of adhesive added.
Often laminate webs are intended to combine properties of the constituent layers to achieve synergistic benefits. For example, EP-B-715,571 issued to Wadsworth discloses a multilayered nonwoven composite web intended for use as a substitute for a woven web such as a textile web. The web comprises at least a layer of thermoplastic man-made fibers and a layer of cellulose-based fibers. The cellulose-based fiber layer is disclosed as thermally bonded to the thermoplastic man-made fiber layers at spaced apart locations. However, it appears that thermal bonding between both, or all, the layers is necessary to produce the requisite bonding.
EP-A-112,654 issued to Haq, et al. discloses a laminate comprising two sheets of nonwoven fabric or the like having sandwiched between them a solid core material which may be a highly porous, optionally liquid-containing, polymer. The two outer sheets are bonded to each other, without involving the core material, by means of a plurality of small, spaced bonding points, for example, spot-welds. Preferably the core material is in continuous sheet form and is perforated to accommodate the bonding points. However, it appears it would present a significant processing problem to register the perforations of the core material in order to have the outer layers bonded therethrough.
For many purposes it is desirable to have an apertured nonwoven web, the apertured web being characterized by a plurality of openings, or perforations, in the web. Such apertures can provide for an open mesh appearance, as well as beneficial texture and cloth-like properties. Such apertured nonwoven webs can be made by methods known in the art. For example, EP-B-164,740 issued to Shimalla discloses an apertured non-woven fabric comprising a web of thermoplastic fibers is described. The fabric is formed with a multiplicity of fused patterned regions and adjacent substantially non-fused regions, there being apertures formed within a plurality of the fused patterned regions but not within the adjacent regions. The fabric is produced by heat embossing a non-woven web of thermoplastic fibers at a temperature above the softening point of the fibers whereby the regions of the web compressed by the projections of the embossing means become fused, and immediately thereafter drafting the embossed web so that apertures are formed in the fused patterned regions. However, it is not apparent that the method disclosed would produce a laminate of nonwoven webs, or a laminate of dissimilar materials.
Another beneficial method of aperturing a nonwoven web, including laminates of nonwoven webs is disclosed in EP-A-852,483, issued to Benson et al. Disclosed is a laminate material having, for example, at least one layer of a spunbonded web joined to at least one layer of a meltblown web, a bonded carded web, or other suitable material. Such apertured webs are useful as the topsheet in a disposable absorbent article. However, this disclosure does not teach laminating webs comprising dissimilar materials (e.g., materials of different material classes or having differing material properties).
A perforated multilayer elastic coversheet comprising an intermediate elastic layer between upper and lower nonwoven layers is disclosed in EP-A-784,461 issued to Palumbo. The upper and lower layers are connected to the intermediate layer only around the perimeters of the perforations. While providing an apertured, elastic laminate, it is not apparent that the method disclosed could produce laminates comprising thermally-dissimilar materials.
As mentioned, nonwoven webs are beneficial components of consumer products, which can include disposable absorbent garments, non-absorbent disposable garments, durable garments, automotive components, upholstered furniture, filtration media, and other consumer or commercial goods. Nonwovens used in these and other applications benefit from their wide range of visual and tactile properties. However, in many cases, the nonwovens used could benefit from being a carrier for other ingredients. For example, it would be beneficial to have a laminate web that is capable of delivering active substances, such as perfumes or insect repellents. Or the laminate web could simply be a carrier for components such as seeds for agricultural use, or odor controlling substances.
Accordingly, it would be desirable to have laminate web carriers of encapsulated substances.
Additionally, it would be desirable to have laminate webs of dissimilar material properties which are not dependent upon thermal compatibility of each constituent layer for structural integrity, and which are capable of providing an additional benefit beyond simple visual and tactile properties.
A substance encapsulation system disclosed. The system comprises a first web and a second web, the first and second webs joined to one another in a face-to-face relationship by at least one bond site defining an elongated melt weakened region having an aspect ratio of at least about 2. The bond site has a longitudinal axis oriented in a first direction and a transverse axis oriented in a second direction orthogonal to the first direction. A powdered, granular, particulate, or gel substance can be disposed between the first and second webs. Upon application of a sufficient force having a vector component parallel to the transverse axis, the bond site fractures to form a corresponding aperture to facilitate exposure of the substance. Alternatively, a central layer may be disposed between at least a portion of the first and second webs. The central layer may carry a substance to be exposed or the central layer may be a dissimilar material from the first and second webs. In a preferred embodiment the system has a plurality of bond sites.